How Much Water Will an Average Bathtub Hold?

Measure your tub to know the volume of water it holds.

Calculate the amount of water in your tub with a few clicks of your calculator. There is no way to calculate the “average” tub size because average means knowing about every tub everywhere, but there are typical tub sizes. The best way to know how much water your tub holds is to measure your own tub. Use the calculations to administer your hot tub chemicals or to know how much Epsom salts to add for that relaxing soak.

Measure

Measure your tub; take all the measurements in inches. Measure the inside width and the inside length. Measure the depth as from the inside bottom of the tub to the bottom of the overflow drain hole. This is the typical fill level.

Multiply

Multiply the width by the length. Multiply the result by the depth. Divide the result by 1,728 for the number of cubic feet of water the tub will hold. Multiply that result by 7.5 for the number of gallons of water held in the tub.

Weight

Bathtubs are available in many sizes, a typical size being 30 inches wide and 60 inches long. The inside measurements of this tub could be 23 inches wide, 15 inches deep to the water level and 54 inches long. This tub holds about 80 gallons of water. If this is an extra deep tub, it might hold up to 110 gallons. Consider that a gallon of water weighs just over 8 pounds; your water alone can weigh almost 700 pounds.

About the Author

Linda Erlam started writing educational manuals in 1979. She also writes a biweekly newspaper column, "Design Dilemmas," in the "Lakeshore News" and has been published in "Design and Drapery Pro" magazine. Erlam is a graduate of the Sheffield School of Interior Design and is a practicing interior decorator and drapery workroom operator.